1. Field of the Invention
This invention relates to electronic data processing systems and more particularly to the remote control and diagnosis of computer systems by means of an external control subsystem.
2. Description of the Prior Art
A computer system for commercial data processing, time-sharing, and/or real-time computing requires a means of communication for its local operator ("operator", as used herein, need not be restricted to human operators but may include other computers or systems for controlling the system referenced) as part of the process of starting, stopping, loading and diagnosing the system. Traditionally, the means of communication has been two-fold, a panel of lamps and switches for manually interacting with the system hardware and a typewriter-like device or console which has traditionally been constrained to interact only with the system software, usually the operating system software. In "remote trouble-shooting", a similar means is required to allow remote operator control capable of operating over a telecommunications channel and it is necessary to combine in this means of communication, both control of software related events and hardware related events. Remote trouble shooting is a useful tool, practically and economically as it allows highly skilled maintenance personnel to attend large numbers of computer systems over wide geographic areas.
The use of a telecommunications channel for control of hardware and software imposes constraints on the nature of the control operations which are possible and the manner in which they are implemented. A telecommunications device, for example, is intrinsically serial in nature. Therefore, the control protocol must be organized such as to be meaningful in terms of the succession of serial events whether those consist of a single input character or a string of input characters. Characters, in this sense, may mean a binary code generated by a remote telecommunications device.
The serial nature of the communications introduces a sensitivity to error because of the characteristics of typical communications paths, and therefore the control mechanism or control protocol must be organized so as to have limited sensitivity to the kinds of error which normally occur in a communications environment. These errors amount to alteration of bits in individual characters, interruption of communications because of noise on the lines, and other such distortions of the information. A consequence of the organization of a computer system for remote control and diagnosis is the need for a central point of control on the system. That point of control is central from the standpoint of the local operator, and the remote point of control must correspond to the point of control of the local operator so that transactions may be monitored, entered or controlled from a remote point and so that control of the computer both in a hardware and a software sense may be had over a single communications path.
It is desirable to have the capability of single point hardware and software control over a communications channel in order to provide maintenance to the computer system in both the case of unanticipated system failures and for preventative or diagnostic purposes where no known failure exists but it is desired to examine the state of the system to see if there are indications of potential failures. In the case where the system itself has failed, an inoperative system cannot control itself and the objective of diagnosing the failure in the machine in order to plan the appropriate maintenance action is defeated. If the system is partially functioning, fault conditions in the system itself may be such as to prevent the use of a control mechanism to diagnose the nature of the fault. Additionally, diagnosis of a failed computer system may be extremely difficult if the existing fault condition requires interactions at a rate faster than is possible over a standard telecommunications interface.
In order to overcome the problems of control and diagnosis of computer systems as described above, the instant invention provides a command and control processor which is able to exercise control of the essential system without being controlled, itself, by the system. The command and control processor will have in it the capability to communicate over a telecommunications path and a capability of receiving, storing, and translating commands from a remote operator into command sequences related to the detailed hardware of the machine. The internal control structure of the system is likewise altered such that the traditional panel of lamps and switches is no longer necessary to the control of the system, creating an economic saving. The lack of physical constraints of lamps and switches also allows the expansion of the number of control points without economic and physical constraints. Information may further be output from the system in larger quantities and greater variety than would be economically feasible through lamp displays, since the potential for data output over a telecommunications path to a telecommunications device is virtually unlimited in quantity and variety of information which can be transferred.
The introduction of a command and control processor in the system also allows the performance of sequences of operations which would not be manually feasible either through the panel of lamps and switches or over a telecommunications panel if it is assumed that the command and control processor operates at electronic speed and is interfaced to the system in such a way that it can control internal conditions at electronic speeds.